Many industrial systems generate harmful radiation during operation, which demands safety precautions for the protection of equipment operators. For example, systems that generate and use x-rays require various types and quantities of shielding to limit or prevent exposure to humans and/or animals. The shielding usually includes strategically placed high atomic weight materials to absorb or block the radiation before exiting the equipment and exposing users in the vicinity. Such shielding, however, can be costly and difficult to incorporate into or on the equipment.
FIG. 1 is an example high vacuum system 100 that includes x-ray shielding. The system 100 may generate x-rays in the high vacuum chamber. In some examples, the x-rays are generated due to electron beam interaction with a metal, for example. The x-ray shielding is placed in and around a vacuum tube coupling a high vacuum chamber to a vacuum pump to block x-rays from exiting the chamber. In general, the generated x-rays may be emitted in any of the 47 steradians, but x-rays directed toward the vacuum tube may be of most concern due to the complexities of providing x-ray shielding to the juncture of the chamber and the vacuum tube. The x-rays emitted toward the vacuum tube may be from various angles, which may be due to direct emission from the electron beam/metal interaction or due to reflections within the chamber. If the x-ray shield was not present, however, x-rays may pass through the chamber wall and/or the vacuum tube wall, which is not desirable. A further concern with the vacuum tube is the need for vacuum pump access to the chamber for obtaining a high vacuum environment while still shielding for x-rays. The need to include the x-ray shield in and around the vacuum tube/chamber junction creates a tradeoff between vacuum conductance and x-ray safety. Vacuum conductance being a measurement of how quickly the chamber may be evacuated to a desired pressure and the ultimate pressure in the high vacuum chamber, for example.
One technique to reduce or eliminate instances of x-rays escaping the chamber and/or vacuum tube is to include the x-ray shielding shown in FIG. 1. The x-ray shielding includes portions outside of the walls of the chamber and the tubing, portions inside at least a portion of the tubing, and a disc placed in front of the tubing. The front view shows the two components of the x-ray shielding with the patterned area being the open area for gas flow during pumping. The arrangement of the disc in front of the tubing essentially creates a labyrinth for the x-rays emitted toward the vacuum tube to travel through before entering the vacuum tube. However, this is also a labyrinth for the gas molecules in the high vacuum chamber to travel to be removed by the vacuum pump. The labyrinth created by the x-ray shielding, at least as it affects gas molecules, reduces the vacuum conductance of the system. The reduction in vacuum conductance results in slower pump times, which may be addressed using more powerful vacuum pumps, and a higher vacuum pressure in the high vacuum chamber than with a good conductance towards it (in the molecular flow regime). Yet, such a solution may at least affect costs, space requirements, and add undesirable vibrations. As such, effective x-ray shielding that allows for increased vacuum conductance is desirable.